The essential concept here is "voluntary". An "agreement" where one or more of the parties was compelled to sign because of duress or undue influence can be invalidated.
In Islam, rejecting the jurisdiction of a Sharia court where one is available makes one an apostate. Apostates are marked for death in Islamic communities. At minimum, they are shunned.
No Muslim woman, especially one living in a heavily Muslim community, can be considered able to freely consent to Sharia jurisdiction because of the strong elements of duress present.
There is a movement to make the teaching of the concept of heaven and hell to young children a form of emotional child abuse. The argument is remarkably the same as the argument you make here -- that people, especially the younger people, but also all people who would fall for religion, are easily led, can easily be pushed under duress to accept whatever beliefs they are told.
And by telling a young child that they could die and go to a place of fire and brimstone, you are emotionally scarring them, in order to force them to accept your religion.
There is a good reason to keep government out of ANY judgment of religion -- because they ARE coming for the Christians. They are warming up on the minor religious practices, and like in WW2, if we don't stand up for the rights of all to make stupid decisions about their own religious beliefs, when they are ready to persecute US, there will be nobody else left to help defend our liberty.
I fully support laws in this country that will prosecute people for murder if they kill others, for whatever reason. That would hold true for "apostates" marked for death, for kids who don't join the right gang and are marked for death, for people who draw pictures of Mohamed, for people who testify against killers in court.